Many devices require post-fabrication trimming in order to operate within specifications. In particular, sensors and references (e.g., frequency references) require such trimming. For the case of macroscopic devices that are manufactured serially, trimming often does not comprise an overwhelming percentage of the total device cost. For the case of microscopic devices fabricated in batches (e.g., integrated circuits or micromechanical devices), trimming or programming can constitute a dominant percentage of device cost if it must be done serially. For example, laser trimming of micromechanical resonators to achieve a specific resonance frequency usually must be done serially, and thus, has low throughput and high cost.
With the advent of frequency specific applications for micromechanical resonators, such as oscillator references and highly selective bandpass filters, techniques for post-fabrication trimming of resonance frequencies are becoming increasingly important. This is especially true for recent communications applications of micromechanical resonators, in which large numbers of such resonators with precisely located center frequencies must realize parallel filter banks and multiple oscillator references. Since these applications will likely be batch-fabricated using planar technologies, high throughput trimming is desirable.
It is known that rapid thermal annealing (RTA) can change stress profiles in polysilicon thin films.